Thieves broke into vans and stole tools being used by a team working on a life-changing project for TV show DIY SOS.
Builders working on the BBC programme were targeted while helping with the project in West Bromwich. Show bosses said three vans have been hit in the past week.
Volunteers are transforming the family home of a mother who died from cancer.
Presenter Nick Knowles tweeted on Wednesday to say he was "really disappointed" by the thefts.
The programme is extending the home of Sandra Chambers, who has looked after her two grandchildren since the death of their mother Crystal in October 2015.
Show bosses said two vans - a Peugeot and a Ford - were broken into on Wednesday morning and tools taken.
On Thursday a Mercedes Sprinter was also broken into, but nothing was stolen. The thefts have been reported to West Midlands Police.
Really disappointed had two volunteer builders Vans broken into on West Brom SOS - damage to Peugeot rear van door - can local dealer mend?— Nick Knowles (@MrNickKnowles) July 26, 2017
Mr Knowles' tweet prompted a local Peugeot dealership to get in touch and he later thanked them for their help, as well as another person who gave £30 to cover repairs.
The project to extend the house is being completed by the DIY SOS team and an army of volunteers, including local tradespeople and neighbours, in a nine-day build.